add webpack to documentation (#22423)

* add webpack to documentation"

implementing PR comments

implementing PR comments

* replace tether with popper

docs/_data/nav.yml

@@ -8,6 +8,7 @@
     - title: Options
     - title: Build tools
     - title: Best practices
+    - title: Webpack
     - title: Accessibility
 
 - title: Layout

docs/getting-started/webpack.md

@@ -0,0 +1,106 @@
+---
+layout: docs
+title: Webpack
+description: Learn how to install Bootstrap using webpack 2
+group: getting-started
+---
+
+Use [webpack v2.x](https://webpack.js.org/) to bundle Bootstrap into your project.
+
+
+## Contents
+
+* Will be replaced with the ToC, excluding the "Contents" header
+{:toc}
+
+## Installing Bootstrap
+
+[Install bootstrap](/getting-started/download/#npm) as a node module using npm.
+
+## Importing JavaScript
+
+Import [Bootstrap's JavaScript](/getting-started/javascript/) by adding this line to your app's entry point (usally `index.js` or `app.js`):
+
+{% highlight js %}
+import 'bootstrap';
+{% endhighlight %}
+
+Alternatively, you may **import plugins individually** as needed:
+
+{% highlight js %}
+import 'bootstrap/js/dist/util';
+import 'bootstrap/js/dist/dropdown';
+...
+{% endhighlight %}
+
+Bootstrap is dependent on [jQuery](https://jquery.com/) and [Popper](https://popper.js.org/), so npm will install them for you if needed. But they must be explicitly provided by webpack. Add the following code to the `plugins` section in your webpack config file:
+
+{% highlight js %}
+  plugins: [
+    ...
+      new webpack.ProvidePlugin({
+        $: 'jquery',
+        jQuery: 'jquery',
+        'window.jQuery': 'jquery',
+        Popper: ['popper.js', 'default'],
+        // In case you imported plugins individually, you must also require them here:
+        Util: "exports-loader?Util!bootstrap/js/dist/util",
+        Dropdown: "exports-loader?Dropdown!bootstrap/js/dist/dropdown",
+        ...
+      })
+    ...
+  ]
+{% endhighlight %}
+
+{% callout warning %}
+Notice that if you chose to **import plugins individually**, you must also install [exports-loader](https://github.com/webpack-contrib/exports-loader)
+{% endcallout %}
+
+## Importing Styles
+
+### Importing Precompiled SASS
+
+To enjoy the full potential of Bootstrap and customize it to your needs, use the source files as a part of your project's bundling process. 
+
+First, create your own `_custom.scss` and use it to override the [built-in custom variables](/getting-started/options/). Then, use your main sass file to import your custom variables, followed by Bootstrap: 
+{% highlight scss %}
+@import "custom";
+@import "~bootstrap/scss/bootstrap";
+{% endhighlight %}
+
+For Bootstrap to compile, make sure you install and use the required loaders: [sass-loader](https://github.com/webpack-contrib/sass-loader), [postcss-loader](https://github.com/postcss/postcss-loader) with [Autoprefixer](https://github.com/postcss/autoprefixer#webpack) and [postcss-flexbugs-fixes](https://github.com/luisrudge/postcss-flexbugs-fixes). With minimal setup, your webpack config should include this rule or similar:
+ 
+{% highlight js %}
+  ...
+  {
+    test: /\.(scss)$/,
+    use: [{
+      loader: 'style-loader', // inject CSS to page
+    }, {
+      loader: 'css-loader', // translates CSS into CommonJS modules
+    }, {
+      loader: 'postcss-loader', // Run post css actions
+      options: {
+        plugins: function () { // post css plugins, can be exported to postcss.config.js
+          return [
+            require('precss'),
+            require('autoprefixer')
+          ];
+        }
+      }
+    }, {
+      loader: 'sass-loader' // compiles SASS to CSS
+    }]
+  },
+  ...
+{% endhighlight %}
+
+### Importing Compiled CSS
+
+Alternatively, you may use Bootstrap's ready-to-use css by simply adding this line to your project's entry point:
+
+{% highlight js %}
+import 'bootstrap/dist/css/bootstrap.min.css';
+{% endhighlight %}
+
+In this case you may use your existing rule for `css` without any special modifications to webpack config.